1. Field of the Invention
The invention relates generally to a process for preparing a biomass/catalyst composite material in the form of fluidizable particles, and more particularly to a thermal treatment step for use in such a process.
2. Description of the Related Art
WO 2007/128800 describes a process for catalytic conversion of biomass material. Particles of solid biomass material are brought into intimate contact with a particulate catalytic material. Further processing of the composite requires reduction of the particle size of the biomass material. Due to the resilient nature of biomass material such particle size reduction requires significant amounts of mechanical energy.
Bridgeman et al., Fuel 87 (2008) 844-856, describes a torrefaction process wherein reed canary grass, wheat straw and willow are treated to enhance the solid fuel qualities and combustion properties of these biomass materials. Torrefaction is defined as “a thermal treatment that occurs in an inert atmosphere. It removes moisture and low weight organic volatile components and depolymerizes the long polysaccharide chains, producing a hydrophobic solid product with an increased energy density and greatly increased grindability.” According to this publication, the material is particularly suitable for co-firing with coal in existing power stations.
Gómez et al., J. Anal. Appl. Pyrolysis 80 (2007) 416-426, describes a thermogravimetric/mass spectrometry study of woody residues and an herbaceous energy crop (artichoke thistle). Samples were heated to temperatures up to 800° C. The publication attempts to simplify the large data set of results by applying a Principal Component Analysis (PCA). Inorganic matter present in the samples appeared to have a catalytic effect on the charring reaction.
Bergman et al., in a paper presented at “The 2nd World Conference and Technology Exhibition on Biomass for Energy, Industry and Climate Protection” in Rome, Italy, 10-14 May 2004, report on the effects of torrefaction on the grindability of biomass. The paper defines torrefaction as “a thermal treatment at a temperature of 200 to 300° C., at near atmospheric pressure and in the absence of oxygen.” The paper concludes that torrefaction may contribute to the technical and economic feasibility of entrained-flow gasification of biomass using existing conventional feeding technology.
These publications do not address the need for preparing liquid fuel products from biomass material.
Thus, there is a particular need for using torrefaction in preparing solid biomass for catalytic conversion to liquid products. There is a further need for preparing solid biomass material for conversion in a catalytic process involving a fluidized bed reactor.